Midas Magic is a mod that now add more than 200 spells, and all different than the normal oblivion spell system.It includes 16 Astral Planes to explore, but you will have to discover them.Only go to the midas shop in the Arcane University.You will have to buy the books and read them to understand, but you will have to read all that midas have to sell and go to the shop basement to go to the astral plane.I don't know how to get the floating isle, because i used the tcl console comand.Read the description in the download link to learn more or se in youtube.

Although this is listed as a companion mod, there is a ton of other stuff you can do, namely the the Underdark. This mod combines the best of two worlds: Companion and Quests. I personally enjoy this mod and hope you will, too.